FIG. 19 is a sectional view illustrating a conventional apparatus for separating a wafer from a support substrate. FIG. 20 is a sectional view of a wafer adhered to a support plate.
In FIG. 20, a wafer 1 is adhered to a support plate 2, such as a glass plate, with a thermally softened adhesive 209, such as wax. Hereinafter, the wafer 1 with the glass plate 2 is called a work 20. Reference numeral 3 designates a metal projection formed at the periphery of the boundary between the wafer 1 and the glass plate 2 due to vapor-deposition or plating.
In FIG. 19, the work 20 is interposed between a lower plate 201 and an upper plate 204. A lower plate 201 includes an upper surface 201a in contact with the wafer 1 of the work 20 and a plurality of openings 201b at the upper surface 201a. These openings 201b are connected to a tube 202, and the tube 202 is connected to an external vacuum pump (not shown). Since air is evacuated through the openings 201b by the vacuum pump, the wafer 1 is held against the upper surface 201a of the lower plate 201. A heater 203 is buried in the lower plate 201.
The structure of the upper plate 204 is identical to the lower plate 201. That is, the upper plate 204 includes a lower surface 204a in contact with the glass plate 2 of the work 20 and a plurality of openings 204b at the lower surface 204a. These openings 204b are connected to a tube 205, and the tube 205 is connected to an external vacuum pump (not shown). Since air is evacuated through the openings 204b by the vacuum pump, the glass plate 2 is held against the lower surface 204a of the upper plate 204. A heater 206 is buried in the upper plate 204. Furthermore, an end of a shaft 207 is fixed to the upper surface of the upper plate 204, and the other end is fixed to a handle 208.
A description is given of the operation.
Initially, a wafer 1 (diameter: 76 mm, thickness: 600 .mu.m) having a front surface on which circuit elements are disposed is adhered to a glass plate 2 using wax 209 so that the front surface of the wafer 1 is in contact with the glass plate 2, whereby the wafer 1 is reinforced. Then, the wafer 1 is ground from the rear surface until the thickness of the wafer is several microns to several hundreds of microns. Thereafter, a metal pattern is formed on the rear surface of the wafer 1 by plating or the like. In the plating process, a metal projection 3 is grown at the periphery of the contact part between the wafer 1 and the glass plate 2 as shown in FIG. 20.
After the process on the rear surface of the wafer 1, an operator puts the work 20 on the upper surface 201a of the lower plate 201 by hand. Since air is evacuated through the openings 201b of the lower plate 201 by the vacuum pump, the wafer 1 is fixed to the surface 201a. At the same time, the lower plate 201 is heated by the heater 203.
Then, the operator takes the handle 208 of the upper plate 204 and puts the upper plate 204 on the glass plate 2 of the work 20. Since air is evacuated through the openings 204b of the upper plate 204, the support plate 2 is held against the lower surface 204a of the upper plate 204. The upper plate 204 is heated by the heater 206.
The work 20 is heated for a prescribed time to soften the wax 209 between the wafer 1 and the glass plate 2 and, thereafter, the handle 208 is moved in the direction indicated by the arrow in FIG. 19, whereby the glass plate 2 is separated from the wafer 1. Then, the operator manually disconnect the wafer 1 and the glass plate 2 from the lower plate 201 and the upper plate 204, respectively, followed by subsequent process steps.
In the above-described conventional apparatus, when the glass plate 2 is separated from the wafer 1, the wafer 1 is flawed or cracked due to the metal projection 3, whereby the wafer is broken in the wafer separating step or in the subsequent steps, such as a wafer washing step.